Blind spots in Doom reject tables

This analysis is based on the stock REJECT lumps in the Ultimate Doom IWAD, and the same lumps rebuilt using RMB 3.0 with the -perfect option. A "blind spot" is defined as any bit which is 1 in the first file but 0 in the second file. Since RMB ignores all height differences between sectors, many of these can be justified as speed optimizations or as tweaks to match the "3D" topography of the level, but certain cases do produce unintentional special effects, as in E1M6.

No anomalies are present in, , , or. The latter is most likely a result of the mapper, John "Dr Sleep" Anderson, using RMB himself to build the reject table.

Explanation
A REJECT table is used by Doom to simplify line-of-sight checking when testing if a monster should see the player and wake up, or if the monster can try and use a ranged attack against the player. A "blind spot" in the REJECT table typically means that two sectors are incorrectly marked as not being visible from one another, making monsters in one sector unable to see actors in the other sector.

This can provide an advantage to the player; as long as they are in one sector and the monster is in the other one, the "blindness" prevents the monster from being woken up, or from attacking the player. In practice, as seen below, in most cases the advantage is negligible.